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  • 1
    ISSN: 1432-0983
    Keywords: Candida maltosa ; mtDNA ; Physical and genetic map
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Mitochondrial (mt) DNA of the ascomycetous yeast Candida maltosa was isolated and characterized. The mtDNA is circular and the size estimated from restriction analysis performed with 7 endonucleases was 52 kb pairs. A restriction map was constructed, using the cleavage data of four endonucleases. Using mt genes from Saccharomyces cerevisiae, six structural genes (large rRNA, apocytochrome b, cytochrome c oxidase subunit I and subunit 11, ATPase subunit 6 and subunit 9) were located on the C. maltosa chondriome by cross hybridization experiments. The comparison between the mt genomes of C. maltosa and six other yeasts showed differences in the overall genome organization.
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  • 2
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Mutants of Candida maltosa were isolated that lacked saccharopine reductase (lys9) and saccharopine dehydrogenase (lys1) and were able to accumulate α-aminoadipate-δ-semialdehyde (AASA) in the cell and excrete it into the culture medium. The effects of incubation time, lysine concentration, and carbon and nitrogen sources on AASA production were examined. In the presence of 15 g glucose/1, 1.25 g NH4H2PO4/l and 50 mg l-lysine/l in a minimal salt medium C. maltosa G285 (lys1) produced about 80–90 mg AASA/l during 48 h of growth. A simple and rapid procedure to isolate AASA from the medium using Dowex 50X4 is described.
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  • 3
    ISSN: 1432-072X
    Keywords: Candida maltosa ; Glyphosate ; Shikimate pathway ; 5-Enolpyruvylshikimate 3-phosphate synthase ; 5-Dehydroquinate synthase ; 3-Deoxy-D-arabino-heptulosonate 7-phosphate synthase ; Enzyme inhibition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The broad-spectrum herbicide glyphosate inhibits the growth of Candida maltosa and causes the accumulation of shikimic acid and shikimate-3-phosphate. Glyphosate is a potent inhibitor of three enzymes of aromatic amino acid biosynthesis in this yeast. In relation to tyrosine-sensitive 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase and dehydroquinate synthase, the inhibitory effect appears at concentrations in the mM range, but 5-enolpyruvylshikimate 3-phosphate (EPSP) synthase is inhibited by micromolar concentrations of glyphosate. Inhibition of partially purified EPSP synthase reaction by glyphosate is competitive with respect to phosphoenolpyruvate (PEP) with a K i -value of 12 μM. The app. K m for PEP is about 5-fold higher and was 62 μM. Furthermore, the presence of glyphosate leads to derepression of many amino acid biosynthetic enzymes.
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  • 4
    ISSN: 1432-072X
    Keywords: Pichia guilliermondii ; Chorismate mutase ; Tryptophan auxotrophy ; Regulatory mutant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have isolated the tryptophan auxotrophic mutant strain, PK101, of Pichia guilliermondii. This strain is not defective in any of the tryptophan biosynthetic enzymes, but its chrismate mutase, an enzyme of the phenylalanine-tyrosine biosynthesis, is changed. In comparison with the wild type chorismate mutase, the enzyme of PK101 is characterized by a complete loss of sensitivity to l-phenylalanine inhibition and to a considerable loss of sensitivity to l-tryptophan activation. Furthermore, the chorismate mutase activity of the mutant is more than 7-fold higher in the absence of l-tryptophan than in the wild type. The PK101 enzyme is also changed in the pH optimum and in some kinetic constants. We found an increased intracellular pool of both phenylalanine and tyrosine and a reduced contents of tryptophan in the mutant cells. Our genetic data indicate that the mutant phenotype is dominant over the wild type.
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  • 5
    ISSN: 1432-072X
    Keywords: Candida maltosa ; Lysine degradation ; Acetyl-CoA:L-lysine N-acetyltransferase ; Enzyme induction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The yeast Candida maltosa can utilize L-lysine as sole nitrogen and sole carbon source accompanied by accumulation of ε-N-acetyl-L-lysine, indicating that lysine is metabolized by way of N-acetylated intermediates. A novel lysine acetyltransferase catalyzing the first step in this pathway, the N-acetylation of the ε-amino group of L-lysine, was found in this yeast. The enzyme, acetyl-CoA:L-lysine N-acetyltransferase, is strongly induced in cells grown on L-lysine as sole carbon source. The enzyme is specific for both L-lysine and acetyl-CoA. The K m values are 10 mM for L-lysine and 0.33 mM for acetyl-CoA. The enzyme has a maximum activity at pH 8.1.
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  • 6
    ISSN: 1432-072X
    Keywords: Saccharomyces cerevisiae ; Acetyl-CoA ; l-Lysine N6 ; acetytransferase ; Lysine catabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The carbon catabolism of l-lysine starts in Saccharomyces cerevisiae with acetylation by an acetyl-CoA: l-lysine N6-acetyltransferase. The enzyme is strongly induced in cells grown on l-lysine as sole carbon source and has been purified about 530-fold. Its activity was specific for acetyl-CoA and, in addition to l-lysine, 5-hydroxylysine and thialysine act as acetyl acceptor. The following apparent Michaelis constants were determined: acetyl-CoA 0.8 mM, l-lysine 5.8 mM, dl-5-hydroxylysine 2.8 mM, l-thialysine 100 mM. The enzyme had a maximum activity at pH 8.5 and 37°C. Its molecular mass, estimated by sodium dodecyl sulphate-polyacrylamide gel electrophoresis, was 52 kDa. Since the native molecular mass, determined by gel filtration, was 48 kDa, the enzyme is a monomer.
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  • 7
    ISSN: 1617-4623
    Keywords: Pathway ; Gene cloning ; Karyotyping ; Mapping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The four enzymatic steps in the conversion of α-ketoisovaleriate to leucine were examined in the wild type and in 13 leucine auxotrophic strains of Candida maltosa. The genetic lesions in the auxotrophs, involve at least five different loci and are correlated with three enzymatic steps. This was confirmed by gene cloning, protoplast fusion, and enzyme assays. The pathway for leucine biosynthesis in C. maltosa shows general similarity to that of other lower eukaryotes but there are individual differences in the numbers of genes responsible for single enzymatic steps. A disomic state of the chromosomes carrying genes coding for α-isopropylmalate synthase and β-isopropyl-malate dehydrogenase was elucidated.
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  • 8
    ISSN: 0749-503X
    Keywords: Arxula adeninivorans ; AILV1 ; threonine deaminase ; transformation ; homologous integration ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The ILV1 gene of the yeast Arxula adeninivorans LS3 (AILV1) has been cloned from a genomic library, characterized and used as an auxotrophic selection marker for transformation of plasmids into this yeast. One copy of the gene is present in the Arxula genome, comprising 1653 bp and encoding 550 amino acids of the threonine deaminase. The protein sequence is similar (60·55%) to that of the threonine deaminase from Saccharomyces cerevisiae encoded by the gene ILV1. The protein is enzymatically active during the whole period of cultivation, up to 70 h. Maximal activities, as well as protein concentrations of this enzyme, were achieved after cultivation times of 20-36 h.The AILV1 gene is a suitable auxotrophic selection marker in transformation experiments using an Arxula adeninivorans ilv1 mutant and a plasmid containing this gene, which is fused into the 25S rDNA of Arxula adeninivorans. One to three copies of the linearized plasmid were integrated into the 25S rDNA by homologous recombination. Transformants resulting from complementation of the ilv1 mutation can be easily and reproducibly selected and in addition are mitotically stable. Therefore, the described system is preferred to the conventional selection for hygromycin B resistance. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 5 Ill.
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  • 9
    ISSN: 1572-9699
    Keywords: Candida maltosa ; N6-acetyl-L-lysine: 2-oxoglutarate aminotransferase ; lysine degradation ; enzyme induction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A novel aminotransferase catalyzing the second step of lysine catabolism, the oxidative transamination of the α-group of N6-acetyllysine, was identified and characterized in the yeastCandida maltosa. The enzyme was strongly induced in cells grown on L-lysine as sole carbon source. Its activity was specific for both N6-acetyllysine and 2-oxoglutarate. The Km values were 14 mM for the donor, 4 mM for the acceptor and 1.7 μM for pyridoxal-5-phosphate. The enzyme had a maximum activity at pH 8.1 and 32°C. Its molecular mass estimated by sodium dodecyl sulphate-polyacrylamide gel electrophoresis was 55 kDa. Since the native molecular mass determined by gel filtration was 120 kDa, the enzyme is probably a homodimer.
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  • 10
    ISSN: 1572-9699
    Keywords: Pichia guilliermondii ; α-aminoadipate reductase ; homocitrate synthase ; saccharopine dehydrogenase ; saccharopine reductase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The regulatory properties of four enzymes (homocitrate synthase, α-aminoadipate reductase, saccharopine reductase, saccharopine dehydrogenase) involved in the lysine biosynthesis of Pichia guilliermondii were investigated and compared with the regulatory patterns found in other yeast species. The first enzyme of the pathway, homocitrate synthase, is feedback-inhibited by L-lysine. Some other amino acids (α-aminoadipate, glutamate, tryptophan, leucine) and lysine analogues are also inhibitors of one or more enzymes. It is shown that only the synthesis of homocitrate synthase is weakly repressed by L-lysine.
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